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URL: https://oeis.org/A068955

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A068955
Greatest prime factor of n^n - (n-1)^(n-1).
5
3, 23, 229, 151, 431, 776887, 14731, 109, 80317, 275311670611, 19395030961, 10423708597, 968299894201, 19428121, 165218809021364149, 808793517812627212561, 3979203955386313, 588489604729898953429, 2126173979464312447783, 5043293621028391, 90772326303985278570534379
OFFSET
2,1
LINKS
Daniel Suteu and Amiram Eldar, Table of n, a(n) for n = 2..86 (terms 2..62 from Daniel Suteu)
FORMULA
a(n) = A006530(A007781(n-1)).
EXAMPLE
A007781(14) = 10809131718965763 = 3 * 61^2 * 968299894201, therefore a(14) = 968299894201.
MAPLE
a:= n-> max(map(i-> i[1], ifactors(n^n-(n-1)^(n-1))[2])):
seq(a(n), n=2..23); # Alois P. Heinz, Mar 10 2019
MATHEMATICA
a[n_] := FactorInteger[n^n - (n-1)^(n-1)][[-1, 1]]; Array[a, 20, 2] (* Amiram Eldar, Feb 06 2020 *)
PROG
(PARI) a(n) = vecmax(factor(n^n-(n-1)^(n-1))[, 1]); \\ Daniel Suteu, Mar 10 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Mar 11 2002
EXTENSIONS
a(18)-a(22) from Daniel Starodubtsev, Mar 10 2019
STATUS
approved